Effects of defect morphology on the properties of the vortex system in Bi2Sr2CaCu2O8+delta irradiated with heavy ions - art. no. 224502

To study the effects of defect morphology on vortex dynamics, reversible ma gnetization, and e-axis magneroresistance, Bi2Sr2CaCu2O8+delta single cryst als are irradiated with heavy-ions; 0.7-GeV Kr-84, 3.5-GeV Xe-136, 3.8-GeV Ta-181, and 3.1-GeV Bi-209. First, defect morphology is investigated by tra nsmission electron microscope (TEM) observations, which reveals that the fl uctuation of defect radius along the ion path increases with decreasing the electronic-stopping power for the incident ion S-e. The frequency dependen ce of the loss-peak temperature, where the imaginary part of ac susceptibil ity reaches a maximum, shows that the power-law behavior of a Bose-glass tr ansition appears only for the irradiation with [S-e] greater than or simila r to 1.9 keV/Angstrom, where [S-e] is the mean value of S-e in the sample. The magnetic-field dependence of reversible magnetization clearly shows the feature of the recoupling of vortices along the c axis only for Ta and Bi irradiations with [S-e] greater than or similar to 3.3 keV/Angstrom. The ma gnetoresistance along the c axis also reveals that the recoupling of vortic es caused by the production of columnar defects takes place when [S-e] grea ter than or similar to 3.3 keV/Angstrom. The present results demonstrate th at the fluctuation in the defect radius along the ion path suppresses the B ose-glass transition and the recoupling of vortices along the c axis.